Implement a timer for an activity.

I think you want something like this: https://developer.apple.com/documentation/swiftui/progressview/init(timerinterval:countsdown:)

Deleted...

I implemented the timer this way... Only thing not working is invalidating the timer inspite of doing it on the main thread (same thread as firing the timer)

 @IBAction func playOrPauseButtonPressed(_ sender: Any) {
        var timer: Timer? = nil
        timerInterval = habit?.timer
        
        if !play!
        {
            if (timer == nil)
            {
                timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { timer in
                    
                    if self.secondsElapsed <= Int(self.timerInterval!)
                    {
                        self.secondsElapsed = self.secondsElapsed + 1
                        
                        let progress = Float(self.secondsElapsed)/Float(self.timerInterval!)
                        
                        DispatchQueue.main.async {
                            self.timerProgressView.setProgress(progress, animated: true)
                        }
                    }
                    else
                    {
                        DispatchQueue.main.async {
                            timer.invalidate()
                            self.playOrPauseButton.imageView?.image = UIImage(named: "Play")
                        }
                        self.play = false
                        self.secondsElapsed = 0
                    }
                }
            }
            DispatchQueue.main.async {
                self.playOrPauseButton.imageView?.image = UIImage(named: "Pause")
                timer?.fire()
            }
            play = true

        }
        else
        {
            DispatchQueue.main.async {
                self.playOrPauseButton.imageView?.image = UIImage(named: "Play")
                timer?.invalidate()
            }
            play = false
        }
    }

Any help with that second part of invalidating the thread? I see the timer keeps firing and the progress view keeps updating.

Unfortunately I cannot undo the above post marked as answered...

Here is the correct solution with play, pause and stop...

    @IBAction func playOrPauseButtonPressed(_ sender: Any) {
        timerInterval = habit?.timer
        if !play!
        {
            if (timer == nil)
            {
                //make new timer
                timer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: true) { timer in
                    
                    //let timer be fired until time interval
                    if timer.isValid
                    {
                        self.secondsElapsed = self.secondsElapsed + 1
                        
                        let progress = Float(self.secondsElapsed)/Float(self.timerInterval!)
                        DispatchQueue.main.async() {
                            self.timerProgressView.setProgress(progress, animated: true)
                        }
                    }
                    else
                    {
                        DispatchQueue.main.async() {
                            self.playOrPauseButton.imageView?.image = UIImage(named: "Play")
                        }
                        self.play = false
                    }
                }
            }
            DispatchQueue.main.async()
            {
                self.timer?.fire()

                //when timer fires show pause button
                self.playOrPauseButton.imageView?.image = UIImage(named: "Pause")
            }

            play = true
        }
        else
        {
            DispatchQueue.main.async()
            {
                self.timer?.invalidate()
                self.timer = nil
                self.playOrPauseButton.imageView?.image = UIImage(named: "Play")
            }
            play = false
        }
    }
    
    @IBAction func stopButtonPressed(_ sender: Any) {
        DispatchQueue.main.async()
        {
            self.timer?.invalidate()
            self.timer = nil
            self.timerProgressView.setProgress(0, animated: true)
            self.playOrPauseButton.imageView?.image = UIImage(named: "Play")
        }
        play = false
        secondsElapsed = 0
    }
    ```

If i set the timer as nil outside the dispatch block, things dont work. dunno why.